3D hindlimb joint mobility of the stem-archosaur Euparkeria capensis with implications for postural evolution within Archosauria.

Demuth, O E; Rayfield, E J; Hutchinson, J R

Abstract

Triassic archosaurs and stem-archosaurs show a remarkable disparity in their ankle and pelvis morphologies. However, the implications of these different morphologies for specific functions are still poorly understood. Here, we present the first quantitative analysis into the locomotor abilities of a stem-archosaur applying 3D modelling techniques. μCT scans of multiple specimens of Euparkeria capensis enabled the reconstruction and three-dimensional articulation of the hindlimb. The joint mobility of the hindlimb was quantified in 3D to address previous qualitative hypotheses regarding the stance of Euparkeria. Our range of motion analysis implies the potential for an erect posture, consistent with the hip morphology, allowing the femur to be fully adducted to position the feet beneath the body. A fully sprawling pose appears unlikely but a wide range of hip abduction remained feasible-the hip appears quite mobile. The oblique mesotarsal ankle joint in Euparkeria implies, however, a more abducted hindlimb. This is consistent with a mosaic of ancestral and derived osteological characters in the hindlimb, and might suggest a moderately adducted posture for Euparkeria. Our results support a single origin of a pillar-erect hip morphology, ancestral to Eucrocopoda that preceded later development of a hinge-like ankle joint and a more erect hindlimb posture.

Citation

Demuth, O. E., Rayfield, E. J., & Hutchinson, J. R. (2020). 3D hindlimb joint mobility of the stem-archosaur Euparkeria capensis with implications for postural evolution within Archosauria. Scientific Reports, 10(1), 15357

• Journal Article Type: Article
• Acceptance Date: Jul 24, 2020
• Publication Date: Sep 21, 2020
• Deposit Date: Oct 7, 2020
• Publicly Available Date: Oct 7, 2020
• Journal: Scientific Reports
• Electronic ISSN: 2045-2322
• Publisher: Nature Research
• Peer Reviewed: Peer Reviewed
• Volume: 10
• Issue: 1
• Pages: 15357
• Public URL: https://rvc-repository.worktribe.com/output/1375609